Accessing a DataShareExtensionAbility from the FA Model

Overview

Regardless of the FA model or stage model, the data read/write function consists of the client and server.

  • In the FA model, the client uses the DataAbilityHelper class to provide external APIs, and the server uses the DataAbility class to provide database read and write services.

  • In the stage model, the client uses the DataShareHelper class to provide external APIs, and the server uses the DataShareExtensionAbility class to provide database read and write services.

If the client uses the FA model whereas the server is upgraded to the stage model, the client cannot access the server.

To resolve this issue, OpenHarmony provides a solution on the framework side for smooth evolution.

Basic Principles

A compatible method is that DataAbilityHelper determines whether to call the DataShareHelper APIs based on the URI prefix (either DataAbility or DataShare). However, this method requires modification to the URI in the original client code.

Instead of manual modification, OpenHarmony adopts the following processing:

  1. The system attempts to start the DataAbility based on the URI passed in. If the startup fails, the system converts the URI prefix to DataShare and attempts to start the DataShareExtensionAbility.

  2. If the URI does not map to any DataAbility or DataShareExtensionAbility, the startup fails. Otherwise, either the DataAbility or DataShareExtensionAbility is started.

Constraints

  1. When you switch a DataAbility to a DataShareExtensionAbility, only the URI prefix can be modified.FAvsStage-uri

  2. The DataShareHelper class implements only certain APIs of DataAbilityHelper. For details about the APIs, see the table below.

    Table 1 APIs invoked when the FA model accesses a DataShareExtensionAbility of the stage model

API Provided by DataAbilityHelper Provided by DataShareHelper Compatible
on Yes Yes Yes
off Yes Yes Yes
notifyChange Yes Yes Yes
insert Yes Yes Yes
delete Yes Yes Yes
query Yes Yes Yes
update Yes Yes Yes
batchInsert Yes Yes Yes
getType Yes No No
getFileTypes Yes No No
normalizeUri Yes Yes Yes
denormalizeUri Yes Yes Yes
openFile Yes No No
call Yes No No
executeBatch Yes No No